Titanium dioxide is considered to be a white pigment with the best performance in the world at present, which is widely used in industrial fields such as coatings, plastics, paper making, printing inks, chemical fibers, rubbers, cosmetics and the like. The titanium dioxide is prepared by using titanyl sulfate and titanium tetrachloride as the raw material. However, titanium is mainly derived from ilmenite which is an ore mainly used for refining titanium. At present, the titanium tetrachloride or the titanyl sulfate is mainly prepared by chlorination or sulfuric acid method followed by distillation for impurities removal. Chlorination comprises the following steps: high-titanium slags and petroleum coke are mixed at a certain proportion and then crushed, and chlorine is introduced to carry out reaction, in order to generate titanium tetrachloride gas which is then condensed to obtain a liquefied titanium tetrachloride liquid, the latter is filtered and distillated to obtain the titanium tetrachloride finished product. The sulfuric acid method is carried out using sulfuric acid for infiltration of ore to produce a large amount of waste acid and ferrous sulfate.
With the development of society and the energy-saving emission reduction call of the country, research and exploration for the new preparation processes and technologies of the titanium dioxide raw materials are inevitable. The method of dissolving ilmenite with hydrochloric acid has also attracted wide interest. At present, the study on dissolution of the ilmenite with hydrochloric acid is divided into two kinds, one of which is served as the former step of the sulfuric acid method, at the condition of high temperature and low acid ore ratio, impurities in the ilmenite are dissolved out, the titanium is precipitated out in form of metatitanic acid after being dissolved, and used as a raw material for the next step of sulfuric acid dissolution, see such as patents CN 1766137A, CN 101935063A, CN 102602991A, CN 102616842A and the like; the other of which is using hydrochloric acid for acidolysis directly, and then extracting and separating titanium oxychloride out, see such as U.S. Pat. Nos. 3,236,596, 4,269,809, 6,500,396B1, 6,375,923, CN1217298A and the like. Although some work and research has been done at home and abroad for that, as well as certain limitations for the dissolution rate and concentration of the ore, production of the titanium dioxide should be achieved by some high energy consumption steps such as heating, concentration and hydrolysis, and the titanium dioxide raw material product basically exists in the aqueous phase, which is difficult to ensure the purity of the titanium dioxide. Therefore, higher requirements for the highly-efficient preparation of high-yield and high-quality titanium dioxide technology have been put forward.